I have a layout for the blog home page that is set to show six posts with the excerpt and featured image for each.

For the first post, I would like the featured image to be larger (size “large”). I have the logic for that done already, but I don’t know how to tell genesis to make that one, single, featured image larger.

Yes and no. I have already implemented the grid loop. But using a grid as an example, what I want is a full-size post first, then a grid under it. I think I may have solved it however…I’ll report back.

OK, if I tell genesis to use the large image in the UI, I can restrict the image size for smaller images in CSS. A dumb, clumsy, mobile-unfriendly solution but it doesn’t look like genesis has the ability to change this.

Just use 2 widgets on top of each other. Using the plugin http://wordpress.org/extend/plugins/genesis-featured-widget-amplified/ you set different properties for each. The first one to display the latest post and the second display whatever number you want, but set an offset of 1. Each instance will provide you with a choice for the image size you want to use.

Yes and no. I have already implemented the grid loop. But using a grid as an example, what I want is a full-size post first, then a grid under it. I think I may have solved it however…I’ll report back.

I know you’ve already had suggestions on how to implement this, but seeing this comment ^ made me jump in. Another member had a similar question the other day. My solution gave her one full size post with the featured image, and 6 excerpts with the thumbnail size image. You could adjust the thumbnail size image to make them be larger than thumbnail: